The present invention concerns a timepiece having a generator with power reserve indication.
Such a timepiece includes a barrel, in which is housed a spring. Time display members are mechanically coupled to the barrel, as well as an electric energy generator. A regulator circuit is intended to enslave the generator frequency to a reference frequency. Thus the regulator circuit includes switching means arranged for electrically braking the generator during braking periods, when the regulator circuit detects that the generator frequency is higher than the reference frequency.
Such a timepiece, shown in FIG. 1, is known from the prior art, particularly from EP Patent No. 0 762 243 in the name of the present Applicant. The timepiece includes a mechanical energy source, formed by a barrel 1 in which a spring 1a is housed, manually or automatically wound, the winding device not being shown here.
Barrel 1 is mechanically coupled to the magnetised rotor 2a of an electric generator 2 via gear trains 3. Generator 2 includes at least one coil 2b, from which an alternating voltage Ug is generated, when magnetised rotor 2a is driven in rotation, generating a magnetic field symbolised by means of an arrow and to which said at least one coil 2b is coupled.
The terminals of coil 2b (or coils) are connected to a rectifier 4 supplying at output a rectified voltage Ua, for powering regulator circuit 6, which will be examined hereinafter.
Analogue display members of a time-related indication 5, typically a set of hands or any other conventional mechanical time display means, are mechanically coupled to the barrel through gear trains 3 of the movement and are secured in rotation to rotor 2a. The rotational speed of hands 5 is kept at a constant mean value owing to regulator circuit 6, which is for enslaving the generator frequency to a reference frequency, such that the speed of the hands corresponds to the speed required to obtain a correct time indication.
This regulator circuit 6 will not be described in detail here, since those skilled in the art can construct such an enslaving device by referring to the description in Swiss Patent Application No. 686 332 in the name of the present Applicant. However, in order to facilitate comprehension of said circuit, its essential elements and working will be recalled here.
This regulator circuit 6 includes an oscillator 6a stabilised by a clockwork type quartz and a frequency divider 6b bringing the frequency of the oscillator 6a to a frequency that can be used by a logic circuit 6c which, by means of a control signal, controls a switching member 7, for example a transistor, in order to brake generator 2 for the purpose of regulating its frequency to the level of a reference frequency advantageously corresponding to a correct time indication by the display members of time indication 5.
The timepiece according to this Patent document also includes a power reserve indicator device 9. This device includes a counter 9a keeping account of the successive braking signals 8 during a determined time period by means of an additional frequency divider 9b. A memory 9c is connected to the output of counter 9b so as to store the counted data during the determined time period, at the output of which there is connected a decoder 9d converting the stored data into a control signal for incremental display means 9e of power reserve 17, achieved by means of a coloured strip, or a liquid crystal cell. xe2x80x9cIncremental display meansxe2x80x9d means a display 9e including successive marks which are illuminated or appear up to the point corresponding to the value of the quantity being measured or calculated.
One of the main advantages of a timepiece having a generator, is that the use of a traditional mechanical watch movement can be reconciled with quartz precision.
This is why, the solution recommended in EP Patent No. 0 762 243, although working in a suitable manner, nonetheless has the drawback of using incremental display means for the power reserve controlled by an indicator device essentially formed by electronic elements that are additional to those necessary for the working of the regulator circuit. Moreover, these additional electronic elements have the effect of increasing the global consumption of the electronic circuit, which may prove harmful to the accuracy of the time indication.
Further, a solution that consists in integrating a conventional power reserve indication device has the drawback of not using the indications provided during operation of the generator and particularly during the braking periods of the latter.
In order to overcome the drawbacks of the prior art, the idea according to the invention is to provide an analogue power reserve indication while using the indications linked to the operation of the generator without increasing the electric power consumption of the timepiece.
The invention therefore concerns a timepiece of the type defined in the preamble of the description, characterized in that the generator controls means for actuating an analogue power reserve member, via an electric quantity transmitted by electric coupling between the actuating means and the generator, during the braking periods.
According to an advantageous embodiment, the actuating means include a stator and a rotor, and are electrically coupled to the generator via the stator, the latter also being magnetically coupled to the rotor which moves the analogue power reserve display member mechanically between a first position corresponding to the spring being wound to a second position corresponding to the spring being let down.